1. Field of the Invention
The present invention relates to a process for manufacturing a micro-encapsulated cross-linkable hot-melt adhesive coating based on an aqueous paste comprising a micro-encapsulated polyisocyanate dispersion and a commercially available amine-terminated copolyamide or copolyester for the manufacture of a base dot as a strike back barrier in double dot coating. The upper dot comprises an amine-regulated copolyamide for ensuring good bonding to the lower dot. More particularly, the invention relates to a hot-melt adhesive compound for a grid-like coating of fixable interlining materials for the garment industry, in particular for outerwear.
2. Description of the Background
In the interests of solving the problems of reduced washing and dry cleaning resistance of fabrics, as well as weaker adhesion, improved hot-melt compounds have been developed, as have improved coating technologies. Duo dot or double dot coatings are described in patents DEB 22 14 236, DE-B 22 31 723, DE-B 25 36 911 and DE-B 32 30 579, for example.
The coating carriers were improved according to the state of the art in that finer yams with fine-denier single fibers including the microfiber range and synthetic yams such as high bulk acrylic or polyester yarn are used. The fabrics which were originally used have been replaced extensively by stitch-bonded fabrics, wherein the latter materials represent a combination of nonwoven and woven fabrics. These combinations result in very soft, though very open structures which place higher demands on coating methods and hot-melt adhesive compounds, in particular with respect to strike back and bleed-through of the hot-melt adhesive compound.
Because of costs and quality reasons, there has been a noticeable drop in the amount of coating applied per m2 of interlining material. Whereas previously coating quantities of 15 to 20 g/m2 were common, nowadays the coating quantities range from 7 to 12 g/m2.
Despite the small quantities, adequate adhesion and fastness must be guaranteed, that is, the hot-melt adhesive may not penetrate into the interlining, otherwise it is no longer available for actual adhesion.
The investigation leading to the present invention was to find an effective strike back barrier which exhibits high bonding strength, good bonding of the upper dot on the base layer and good washing and dry cleaning resistance, as well as having a sterilizing capacity, with a reduced quantity of coating material. Another advantage would be that a higher level of thermal stability under load is achieved.
The state of the art is such that a range of strike back barriers is known, such as cross-linking acrylate and polyurethane dispersions and powder-filled pastes based on high-melting copolyamides and polyethylene and high-viscosity thermoplastic polyurethane powders. All of these systems have more or less major disadvantages when applied to rough, napped interlinings and in their bonding to the upper dot or in their wash-resistance.
In the case of coatings of self-cross-linking acrylate or polyurethane dispersions, partial cross-linking frequently occurs during coating, which may result in a coating forming on the template and thus blockage of the template holes. Extensive cleaning of the plant is then required. When production-related downtime occurs, the downtime can also cause major difficulties and disturbances to the point that the templates become unusable. Also, when the material is being applied, bonding of the upper dot to the base layer is a problem. The high-viscosity powder-filled systems based on polyamide, polyethylene and polyurethane generally do not satisfy the resistance to strike back that is required.
To date there has been no success in creating a stable cross-linked system for the base dot. The isocyanates preferably used for this purpose were unable to be stabilized against water (matrix for coating pastes) or the activation temperatures required for crosslinking (greater than 150xc2x0 C.) were excessive.
For special applications where the activation temperature can be higher ( greater than 150xc2x0 C.), for example, for fixing shirt collars, internally blocked polyisocyanates, e.g. dimerized polyisocyanates, may be employed. Powder mixtures of this polyisocyanate and the amine-terminated copolyamide or copolyester can also be processed by means of other application techniques such as by powder dispersion or powder dot. At the present time, polyethylene with melting points of 110xc2x0 C. to 120xc2x0 C. or higher-melting polyamides in the melting range of 130xc2x0 C. to 160xc2x0 C. have been used for fixing shirt collars.
Isocyanates have had to be stabilized against water or against diffusion of humidity to ensure activability at relatively low temperatures.
Accordingly, one object of the present invention is to provide an effective strike back barrier which exhibits high bonding strength, good bonding of the upper dot on the base layer even on rough bases and good washing and dry cleaning resistance, as well as a sterilizing capacity with a reduced quantity of coating material.
Another object is to achieve increased thermal stability under load for the hot-melt adhesive coating and to facilitate processing of the dispersions, as well as preventing the templates from becoming blocked.
Still another object of the invention is to clearly improve the sensitivity of the isocyanate to humidity.
Briefly, these objects and other objects of the present invention as hereinafter will become more readily apparent can be attained by a process comprising micro-encapsulating a cross-linking constituent with a silanized polybutadiene, the reactive constituents of the cross-linking constituent has been first reacted in the melt with cross-linking, thereby manufacturing a cross-linkable hot-melt adhesive compound for coating and/or laminating surface formations.